1. Field of the Invention
This invention relates to power supplies and in particular to self oscillating switching regulator power supplies.
2. Description of the Prior Art
Switching regulator power supplies employ a transformer for cyclically storing energy in its magnetic field during an energy storage cycle and then transferring the energy stored in the magnetic field to secondary windings during an energy transfer cycle. Self-oscillating switching regulator power supplies such as that disclosed and claimed in U.S. Pat. No. 3,889,173 operate over a wide frequency range because the frequency varies approximately inversely with the load. Since the time required for switching is finite, the switching time occupies a greater percentage of the duty cycle as the frequency increases with a resultant loss of efficiency.
It is desirable to increase the period of each switching cycle. However, the frequency must always be high enough to avoid audible noise. Therefore, in order to maximize efficiency, it is desirable to have the switching regulator operating frequency approximately constant above the audible frequency range. Driven regulator power supplies such as the clock controlled regulator disclosed in copending U.S. Patent Application, Ser. No. 502,703, now abandoned entitled "Switching Regulator Power Supply" and assigned to the assignee of this invention, have achieved this. The transformer of this invention makes possible a switching regulator power supply that does not have to rely on a separate clock to operate continuously above the audible range of frequencies.